Supports made of cellulose derivatives for use in the manufacture of sheets of material soluble in organic solvents



Jan. 22, 1935. W, GLADHORN ETAL 1,988,550 SUPPORTS MADE 0E cELLULosE DERIvATIvEs RoR USE IN THE MANUEAGTURE 0E SHEETS oF MATERIAL soLUBLE IN ORGANIC soLvENTs Filed June 4, 1952 com/ejer and' QMM.

UNITED STATE Patented Jan. 22, 1935 SUPPORTS MADE OF CEILULOBE DERIVA- TIVES FOB USE 1N THE MANUFACTUBE -OF SHEETS OF MATERIAL SOLUBLE IN ORGANIC- SOLVENTS Werner Gladhorn, Dessau in Anhalt, Germany, and Leopold Eckier, Binghamton N. Y.,'al

signora to Agfa Anloo Corporation, Binghams PATENT OFFICE ton, N. Y., a corporation of New York Application June 4, 1932, Serial No. 615,428 In Germany October 16, 1926 18Claims.

- rivative, the surface of said layer being insoluble and unswellable in the solvents contained in the said solution.

It is a continuation in part of our application Serial Number 227,043, filed October 18,1927;

One of its lobjects is to provide a process of obtaining such supports. Another objectis the support obtainable by this process. Further objects will be seen from the detailed specification following hereafter. l

It is common practice in the artl to make sheets of any thickness from certain materials by causing a solution of said material in an organic solvent to ilow on a support which consists of a layer of a cellulose derivative. In consequence of the great sensitiveness of cellulose derivatives to the organic solvents used in making the solution which is to flow, the process involves considerable difficulty. The solvent used has a swelling or solvent action on the cellulose derivative support; thus the smoothness of the support and therefore also that of the sheet produced is affected. Furthermore,

the solidied sheet can be separated from the support only with diiilculty because the solvent has brought about to some extent an interunion between the support and thev sheet.

In order to avoid these difdculties it has been proposed to use as the support such cellulose derivatives which are as. 'different as possible frfm the material from which the Asheet is to be made with respect to their solubility in the solvents used. For example, supports of cellulose ethers have been used for receiving a solution of nitro-cellulose for the purpose in question. 'Ihis expedient, however, does not afford supports of suicient resistance because in spite of the differences which exist between the sev eral esters and ethers of cellulose there still takes place an attack of amr such support by the solvent sufficient to prevent the production of a perfect sheet. v

The present invention consists in changing by a suitable treatment the surface of the support consisting of a cellulose derivative that the latter is no longer liable to swell or to dissolve in the organic solvents usually: 'employed for making the casting dope.

A treatment which produces the desired effect consists in superiicially saponifying the cellulose derivative forming the support .or changing in any other way the chemical properties of the latter. Thus, the treatment ac `cording to the invention of supports consisting of a cellulose ether or a cellulose ester produces aLsupercial layer which consists wholly or to the greater part of regenerated cellulose and differs inrits solubility relationships from the cellulose esters and cellulose ethers to such an' extent that the surface ofA the support remains practically unaffected by the usual organic solvents suitable for dissolving cellulose derivatives. Of the numerous cellulose derivatives which are suited for being used in making supports for casting iilms,.iiitrocellulose and cellulose acetate Ihave proved to be of' particular importance. These materials may be used in form of the wastes which are produced inthe manufacture of films and so on. The surface treatment may be effected with any suitable agent, but ammonium sulfhydrate 'or sulfuric acid are preferred for saponifying nitrocellulose and caustic alkalis for the saponication of cellulose acetate. `The agents are generally applied in theiraqueous or alcoholic solution or in mixtures volf alcohols and water. Thev concentration depends essentially upon the emciency of the agent, the duration of treatment and the progress of the attack. Whenusing alkaline agents a concentration between 2 and 10 per cent will be sufllcient in most cases, when saponifying nitro Y cellulose with sulfuric acid a concentration of 80-90 per cent will be employed, however, our

invention Vis not limited to these concentrations.

A superficial saponlcation will often be sumcient but then the surface is very easily injured, thus we prefer to vproduce a saponiiled layer of about 10 to 20 p. thickness, however the saponifieation may be carried farther, if desired.

v'I'he production of the casting support and of the illms is done according toy known meth- The surface of the conveyor band of a casting machine preferably consisting of metal,

for instance, copper-is provided with a coatin the treatment. is removed by washing with water. After drying the sheets, for instance, photographic nlms and the like may be cast in the usual way.

According to another mode of the invention there may be first cast a layer of, for instance, nitrocellulose or cellulose acetate onto the belt or casting surface and on this coating another coating of the same material or another material may be applied, but having other dissolving properties. So, for instance, a basic coating of a cellulose acetate containing about 524 coating which must have a certain thickness can be provided with a coating which is easily removable when damaged and is less thick. l

The saponiiled layer does not wholly consist of regenerated cellulose. Only the surface of this layer may be-of pure cellulose hydrate. In any case the saponiilcation must be carried on so far that the surface of the casting support does not swell under the inuence of the solvents of the solution to be cast. Furthermore the saponied layer has not a homogeneous composition. The content of. for instance, aceticacid of, the. different strata increases steadily from the surface layer towards the belt proper.

The accompanying drawing shows in cross section on an exaggerated scale two embodiments of our invention and is in itself explanatory.

.The following examples serve to illustrate our invention. v

Example 1.-A solution of nitrocellulose containing about 10 to 12% of nitrogen in acetone is applied in known manner to the copper belt of a castingmachineso as toform a coating of 0.5mm. thickness. The conveyor band is then for about 1 hour through an aclueo'usI solution of ammonium sulfhydrate of 10 per cent strength. Hereafter it is washed with water.

. After drying the coating has .a saponiiied surface layerof about 15 u thickness. Films can becastonthissupportintheusualmanner.

Example 2.-A solution of cellulose acetate containing about 52 to 56 percent of acetic acid is applied in known manner to the conveyorbandofacastingmachinesoastoform a coating of about 0.5 mm. thickness. After drying it is subjected to the action of a` 10 percent solution of caustic potash in methanol for about 5 to 10 minutes. Hereafter the remaining lye and the salt formed during the saponincation are removed by with water. 'I'he casting support thus prepared is dried with heated The saponifled volving the steps of applying to a conveyor band of a casting machine an initial layer of a cellufurther treatment iseifected-according to Example 2.

Our invention is no't limited to the foregoing examples or to the specic details given therein. Numerous other embodiments are possible and we contemplate, as included within our invention, all such modifications and equivalents as fall within the scope of the appended claims.

What we claim is: e

- l. In the process of manufacturing sheets the steps which comprise coating the conveyor band of a casting machine with a layer of a cellulose derivative soluble inorganic solvents, and reducing the solubility of the surface strata of said layer in organic solvents by subjecting said.

surface to a chemical treatment adapted to chemically alter said surface.

2. In the process of manufacturing sheets the steps which comprise coating vthe conveyor band of a casting machine with a layer of a Vcellulose derivative soluble in organic solvents,

and saponifying the surface strata of said layer.

3. In a process of making a support of cellulose derivative for use in the manufacture of sheets of material soluble in organic solvents involving the steps of applying to a conveyor band of a casting machine an initial layer of a cellulose derivative soluble in organic solvents and applying thereover an external layer of a cellulose derivative which is sensitive to the organic solvents used in making the solution which is to be cast thereover, the improvement which consists in reducing the solubility of the surface strata of the external layer in organic solvents by subjecting said surface to a chemical treatment designed to chemically alter said surface.

4. In a process of making a support of cellulose derivative for use in the manufacture of sheets of material soluble in organic solvents inlo derivative soluble in organic solvents andv applying thereover an external layer of a cellulose derivative which is sensitive to the organic solvents used in making the solution which is to be cast thereover, the improvement which consists in saponifying he surface strata of said exeternal surface layer.

5. Improved process as defined in claim 3,' characterized in that the external layer consists essentially of-cellulose acetate soluble in organic solvents.

6. Improved process as defined in claim 3, characterized in that the external layer consists essentially` of nitrocellulose soluble in organic solvents.

7. In the process of manufacturing sheets the steps which comprise coating the conveyor band of a casting machine with a layer of nitrocellulose soluble in organic solvents, and saponify'ing the surface strata of said layer.

8.'In the process of manufacturing sheetslthe steps which comprise coating. the conveyor band of a casting machinewith a layer of a cellulose acetate soluble in organic solvents, and saponifying the surface'strata of said layer.

9. In. the process of manufacturing sheets the steps which comprise applying to the copper belt of a casting'machine a solution o f nitrocellulose containing'about'l to 12 per cent of nitrogen in acetone, so as toI form after drying a vcoating of about 0.5 mm; thicknesatreating said coatingfor about 1 hour with a 10 per cent solution of Lacasse ammonium suliliydrate, washing said treated coating and drying the same.

10. In the process of manufacturing sheets the steps which comprise applying to the copper belt of a casting machine a solution of .cellulose acetate containing about 52-56'per cent of acetic acid, so as to form after drying a coating of about 0.5 mm thickness, treating said coating for about to 10 minutes with a 10 per cent solution of caustic 'potash in methanol, washing said treated coating lwith water and drying the same.

11. In the process of manufacturing sheets the steps which comprise applying to the copper belt cent strength so as to form after drying asecond coating of about 0.2 mm thickness, treating said second coating for about 5 to 10 minutes with a per cent solution of caustic potash in methanol, washing said t ted coating with water and drying the same.

12. In the process of manufacturing sheets the steps which comprise coating the conveyor band of acasting machine with a layer of nitro-v derivative the surface strata of which layer havel been chemically treated to reduce the solubility of said surface strata in organic solvents.

14. A castingsupport comprising a conveyor band carrying fan external layer of a cellulose derivative the surface strata of which layer have beensaponied.

15.y A casting support comprising av conveyor band carrying anv external layer of Anitrocellulose the surface strata of which layer have been saponified.

16. A casting support comprising a conveyor band carrying an external layer of cellulose acetate the surface strata of which layer have been saponifled. Y

l1'7. A casting support comprising a conveyor. band, a layer of a cellulose derivative firmlyad haring to said conveyor band and on said layer an outer layer of a cellulose derivative having a solubility different from that of the cellulose de-` rivative constituting said first named layer, said outer layer comprising an internal stratum flrmly adhering to said first named layer and an ex ternal stratum of saponified cellulose derivative integral with said internal stratum.

18. A casting support comprising a c/onveyor band, a layer of cellulose acetate firmly adhering to said conveyor band. and on said layer an outer layer of cellulose acetate having a solubility different from that `of the cellulose acetate constituting said first named layer, said outer layer comprising an internal stratum firmly ad hering to said first named layer and an external stratum. of saponied cellulose acetate integral with said internal stratum. Y.

y WERNER GLADHORN. f-

" LEOPOLD ECKLER. 

